In the field of anatomic pathology, a piece of human tissue is typically inspected and analyzed by marking a sample with a stain that reveals a visual indicator of diagnostic significance and then placing the stained tissue on a slide for viewing under a microscope. Automated imaging systems exist today that capture microscopic image data using a scanning instrument, such as a digital camera in combination with a computer-controlled microscope. Capturing areas of the slide sample at high magnification is necessary for examining minute features of the tissue. A single image of an entire tissue specimen at a high magnification such as 40× requires significant computer storage space and involves lengthy retrieval times. Alternatively, by collecting and storing the sample as any number of contiguous micro images at high objectives, the system can perform various compression techniques and make improvements to data acquisition, retrieval, display, and storage of the images.
A challenge relating to microscopy for anatomic pathology involves assembling micro images captured at high magnifications into a variety of fields of view. This could include a composite image of the entire slide sample or a field of view spanning any portion of the specimen. For example, U.S. Pat. No. 6,404,906, entitled, “Method and apparatus for acquiring and reconstructing magnified specimen images from a computer-controlled microscope,” describes a method of using a computer-controlled microscope system to provide a reconstructed, seamless image from several contiguous fields of view to show the architecture and spatial relationship of biological material in a specimen. A macro image of contiguous image titles at a low magnification and optical resolution is obtained, and the user navigates within the macro image and selects areas. Higher magnification titles for the selected area are assembled and viewed at a higher magnification and optical resolution as a composite micro image of the selected area. Both the macro and micro images may be displayed simultaneously. Preferably, the user may scroll and cause additional fields of view to be added to previously displayed fields of view.
While the '906 patent provides a means of reconstructing micro images into other fields of view, it does not ensure that the system captured the expected image in the first place, nor does it explain what to do if image capture was imprecise. Calibration of such a system is frequently performed, but it is still unfeasible to account for every minor inaccuracy when working with images at very high magnification levels. One example of a calibration inaccuracy in the system might occur while moving the turret from one microscopic image to another. Because this process involves mechanical precision in measurements of microns, a slightly different image from what was expected may be captured. As a result, significant tissue samples may be overlooked. In addition, visible discontinuities may exist for any macro image including micro images where capture was inaccurate. What is needed is a means of seamlessly aligning microscopic images into larger fields of view.
Furthermore, if image capture by an automated microscope system is consistently inaccurate, this may indicate a need to calibrate the system. By analyzing the offset of each image, the system may be able to determine the variable by which inaccuracy is occurring. What is needed is a means of distinguishing between reasonable system inaccuracies and recurring system inaccuracies.